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<h1 class='fqn'><span class='in-band'>Crate <a class="mod" href=''>num_bigint</a></span><span class='out-of-band'><span id='render-detail'>
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</span><a class='srclink' href='../src/num_bigint/lib.rs.html#11-156' title='goto source code'>[src]</a></span></h1>
<div class='docblock'><p>A Big integer (signed version: <code>BigInt</code>, unsigned version: <code>BigUint</code>).</p>
<p>A <code>BigUint</code> is represented as a vector of <code>BigDigit</code>s.
A <code>BigInt</code> is a combination of <code>BigUint</code> and <code>Sign</code>.</p>
<p>Common numerical operations are overloaded, so we can treat them
the same way we treat other numbers.</p>
<h2 id="example" class="section-header"><a href="#example">Example</a></h2>
<pre class="rust rust-example-rendered">
<span class="kw">extern</span> <span class="kw">crate</span> <span class="ident">num_bigint</span>;
<span class="kw">extern</span> <span class="kw">crate</span> <span class="ident">num_traits</span>;
<span class="kw">use</span> <span class="ident">num_bigint</span>::<span class="ident">BigUint</span>;
<span class="kw">use</span> <span class="ident">num_traits</span>::{<span class="ident">Zero</span>, <span class="ident">One</span>};
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">mem</span>::<span class="ident">replace</span>;
<span class="comment">// Calculate large fibonacci numbers.</span>
<span class="kw">fn</span> <span class="ident">fib</span>(<span class="ident">n</span>: <span class="ident">usize</span>) <span class="op">-></span> <span class="ident">BigUint</span> {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">f0</span>: <span class="ident">BigUint</span> <span class="op">=</span> <span class="ident">Zero</span>::<span class="ident">zero</span>();
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">f1</span>: <span class="ident">BigUint</span> <span class="op">=</span> <span class="ident">One</span>::<span class="ident">one</span>();
<span class="kw">for</span> _ <span class="kw">in</span> <span class="number">0</span>..<span class="ident">n</span> {
<span class="kw">let</span> <span class="ident">f2</span> <span class="op">=</span> <span class="ident">f0</span> <span class="op">+</span> <span class="kw-2">&</span><span class="ident">f1</span>;
<span class="comment">// This is a low cost way of swapping f0 with f1 and f1 with f2.</span>
<span class="ident">f0</span> <span class="op">=</span> <span class="ident">replace</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">f1</span>, <span class="ident">f2</span>);
}
<span class="ident">f0</span>
}
<span class="comment">// This is a very large number.</span>
<span class="macro">println</span><span class="macro">!</span>(<span class="string">"fib(1000) = {}"</span>, <span class="ident">fib</span>(<span class="number">1000</span>));</pre>
<p>It's easy to generate large random numbers:</p>
<pre class="rust rust-example-rendered">
<span class="kw">extern</span> <span class="kw">crate</span> <span class="ident">rand</span>;
<span class="kw">extern</span> <span class="kw">crate</span> <span class="ident">num_bigint</span> <span class="kw">as</span> <span class="ident">bigint</span>;
<span class="kw">use</span> <span class="ident">bigint</span>::{<span class="ident">ToBigInt</span>, <span class="ident">RandBigInt</span>};
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">rng</span> <span class="op">=</span> <span class="ident">rand</span>::<span class="ident">thread_rng</span>();
<span class="kw">let</span> <span class="ident">a</span> <span class="op">=</span> <span class="ident">rng</span>.<span class="ident">gen_bigint</span>(<span class="number">1000</span>);
<span class="kw">let</span> <span class="ident">low</span> <span class="op">=</span> <span class="op">-</span><span class="number">10000</span>.<span class="ident">to_bigint</span>().<span class="ident">unwrap</span>();
<span class="kw">let</span> <span class="ident">high</span> <span class="op">=</span> <span class="number">10000</span>.<span class="ident">to_bigint</span>().<span class="ident">unwrap</span>();
<span class="kw">let</span> <span class="ident">b</span> <span class="op">=</span> <span class="ident">rng</span>.<span class="ident">gen_bigint_range</span>(<span class="kw-2">&</span><span class="ident">low</span>, <span class="kw-2">&</span><span class="ident">high</span>);
<span class="comment">// Probably an even larger number.</span>
<span class="macro">println</span><span class="macro">!</span>(<span class="string">"{}"</span>, <span class="ident">a</span> <span class="op">*</span> <span class="ident">b</span>);
</pre>
<h2 id="compatibility" class="section-header"><a href="#compatibility">Compatibility</a></h2>
<p>The <code>num-bigint</code> crate is tested for rustc 1.8 and greater.</p>
</div><h2 id='modules' class='section-header'><a href="#modules">Modules</a></h2>
<table>
<tr class=' module-item'>
<td><a class="mod" href="big_digit/index.html"
title='mod num_bigint::big_digit'>big_digit</a></td>
<td class='docblock-short'>
</td>
</tr></table><h2 id='structs' class='section-header'><a href="#structs">Structs</a></h2>
<table>
<tr class=' module-item'>
<td><a class="struct" href="struct.BigInt.html"
title='struct num_bigint::BigInt'>BigInt</a></td>
<td class='docblock-short'>
<p>A big signed integer type.</p>
</td>
</tr>
<tr class=' module-item'>
<td><a class="struct" href="struct.BigUint.html"
title='struct num_bigint::BigUint'>BigUint</a></td>
<td class='docblock-short'>
<p>A big unsigned integer type.</p>
</td>
</tr></table><h2 id='enums' class='section-header'><a href="#enums">Enums</a></h2>
<table>
<tr class=' module-item'>
<td><a class="enum" href="enum.ParseBigIntError.html"
title='enum num_bigint::ParseBigIntError'>ParseBigIntError</a></td>
<td class='docblock-short'>
</td>
</tr>
<tr class=' module-item'>
<td><a class="enum" href="enum.Sign.html"
title='enum num_bigint::Sign'>Sign</a></td>
<td class='docblock-short'>
<p>A Sign is a <code>BigInt</code>'s composing element.</p>
</td>
</tr></table><h2 id='constants' class='section-header'><a href="#constants">Constants</a></h2>
<table>
<tr class=' module-item'>
<td><a class="constant" href="constant.ZERO_BIG_DIGIT.html"
title='constant num_bigint::ZERO_BIG_DIGIT'>ZERO_BIG_DIGIT</a></td>
<td class='docblock-short'>
</td>
</tr></table><h2 id='traits' class='section-header'><a href="#traits">Traits</a></h2>
<table>
<tr class=' module-item'>
<td><a class="trait" href="trait.RandBigInt.html"
title='trait num_bigint::RandBigInt'>RandBigInt</a></td>
<td class='docblock-short'>
</td>
</tr>
<tr class=' module-item'>
<td><a class="trait" href="trait.ToBigInt.html"
title='trait num_bigint::ToBigInt'>ToBigInt</a></td>
<td class='docblock-short'>
<p>A generic trait for converting a value to a <code>BigInt</code>.</p>
</td>
</tr>
<tr class=' module-item'>
<td><a class="trait" href="trait.ToBigUint.html"
title='trait num_bigint::ToBigUint'>ToBigUint</a></td>
<td class='docblock-short'>
<p>A generic trait for converting a value to a <code>BigUint</code>.</p>
</td>
</tr></table><h2 id='types' class='section-header'><a href="#types">Type Definitions</a></h2>
<table>
<tr class=' module-item'>
<td><a class="type" href="type.BigDigit.html"
title='type num_bigint::BigDigit'>BigDigit</a></td>
<td class='docblock-short'>
<p>A <code>BigDigit</code> is a <code>BigUint</code>'s composing element.</p>
</td>
</tr>
<tr class=' module-item'>
<td><a class="type" href="type.DoubleBigDigit.html"
title='type num_bigint::DoubleBigDigit'>DoubleBigDigit</a></td>
<td class='docblock-short'>
<p>A <code>DoubleBigDigit</code> is the internal type used to do the computations. Its
size is the double of the size of <code>BigDigit</code>.</p>
</td>
</tr></table></section>
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